Increase In Rate Of Autoxidation Research Articles

Structural aspects and physiological implications of the hemoglobin of green iguana (Iguana iguana)

Iguana iguana is a lizard found in South America, and its metabolism is directly related to ambient heat. However, the physiology underlying the effect of temperature change on the metabolism of these reptiles has not been fully elucidated. I. iguana hemoglobin (iHb) was isolated and purified by exclusion chromatography. Mass spectrometry, circular dichroism, SAXS and spectroscopic characterization were used to evaluate the primary and secondary structures and oligomeric state of iHb. The secondary structure of intact iHb, which mainly consisted of α-helices, was not stable if heated at 60 °C. Autoxidation rates of iHb were measured at 30 and 40 °C, revealing a suggestive bi-exponential behavior. Furthermore, by lowering the pH from 7.4 to 6.0, an increase in autoxidation rate was observed, indicating a behavior responsive to metabolic changes. Compared to ATP, ADP showed an allosteric effect on iHb oxygenation by lowering its oxygen binding. Alignment of the amino acid sequences revealed that iHb exhibits conserved substitution of a residue at the allosteric site, suggesting that some unknown molecular mechanism accounts for the allosteric effect caused by ADP. The ability of iHB to oxygenate is directly related to metabolic changes, ensuring the survival of Iguana iguana in different environments.

Autoxidation of brain homogenates from various animals as measured by thiobarbituric acid assay

Introduction The TBARS assay has been well recognized for determination of lipid peroxidation and oxidative injury in biological samples including brain homogenates. In general, the homogenates are freshly prepared using rat brains as the tissue sources. In this study, we compared the rates of spontaneous lipid peroxidation in brain homogenates obtained from bovine, canine, hen, rat, and swine. In addition, the influences of lyophilization process and storage time up to six months at − 20 °C without the freeze–thaw cycle were also determined in the swine brain preparations. Methods The standard assay for thiobarbituric acid-reactive substances (TBARS) was performed at 37 °C, using spectrophotometry to quantify the malondialdehyde (MDA) content. Results Rat brain homogenate exhibited the highest autoxidation rate (0.128 ± 0.002 μM/min) whereas the bovine brain exhibited the lowest rate (0.032 ± 0.001 μM/min). Swine brain homogenate could be kept at − 20 °C up to 3 months without a significant increase in rate of autoxidation. Lyophilization caused a significant increase in the autoxidation rate of brain homogenate. However, the autoxidation rates of the lyophilized preparation were quite comparable throughout the six-month freezing time. Discussion Swine brain was a good candidate for tissue source in the TBARS reaction. The homogenate could be kept in the lyophilized form under the storage condition at − 20 °C without the freeze–thaw cycle in the dark for at least six months.

Control of pro-oxidant activity of cupric ions by entrapment in unilamellar lipid vesicles.

As a demonstration of a potential means of delivering and controlling the biochemical and biological activity of metal ions, cupric ions have been trapped in unilamellar phospholipid vesicles. The activity of these cupric ion-containing vesicles as catalysts of the autoxidation of ascorbate and epinephrine has been investigated. A marked increase in autoxidation rate was observed on release of the cupric ion on addition of detergent. When an azobenzene-containing photochromic lipid was incorporated in the bilayer membrane of the vesicles, the release of cupric ions could be initiated by irradiation with ultraviolet light. In the dark, these vesicles remained stable for at least several weeks. Photo-controlled release of liposomally-entrapped species might find application in areas similar to those where 'caged' reagents are presently used.

Unstable haemoglobin haemolytic crises: contributions of pyrexia and neutrophil oxidants.

Pyrexia and the production of oxidants by phagocytic cells have been examined as two possible causes of haemolytic crises associated with infections in carriers of unstable haemoglobins. Three unstable haemoglobins were examined, both in red cells and after purification. Incubation at 40 degrees C rather than 37 degrees C resulted in only a slight increase in autoxidation rate, but a considerable increase in the rate of precipitation of the haemoglobins as Heinz bodies. Oxidants produced by activated neutrophils were capable of oxidizing haemoglobin both in solution and red cells, though there was no preferential effect on the unstable as opposed to the normal haemoglobin. It is concluded that haemolytic crises associated with infections in carriers of unstable haemoglobins can be explained by increased intracellular precipitation of the haemoglobin as Heinz bodies caused by the accompanying pyrexia.